Reid C16 Spruce

[reidhowdy]

Heaps Practice

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Comprehension Questions

Question	Answer
How is a Heap different from a Binary Search Tree?
Could you build a heap with linked nodes?
Why is adding a node to a heap an O(log n) operation?
Were the heap_up & heap_down methods useful? Why?

[anselrognlie]

✨💫 Nice job on your implementation, Reid. I left some comments below.

You left the comprehension questions blank, and a few of the complexity questions are incomplete, so I'm grading this as a yellow for now. But please feel free to resubmit if you would like a green score!

🟡

[anselrognlie]

👀 Your time complexity looks good, but what about the space complexity?

[anselrognlie]

👀 Prefer using is to compare to None

[anselrognlie]

👀 We have an empty helper we could use here

[anselrognlie]

👀 Again, time complexity looks good, but what about the space complexity?

[anselrognlie]

👀 What are the time and space complexities for empty?

[anselrognlie]

👀 What are the time and space complexities for heap_up?

[anselrognlie]

👀 An empty list is falsy, but what would happens if the list were not empty?

Python would fall off the end of the function, with the default None return value. But since we're returning a boolean from one path, we should be consistent everywhere.

        if not self.store:
            return True
        else:
            return False

which simplifies to

        return not self.store

[anselrognlie]

✨ Nice approach of first determining the candidate child, then deciding whether the swap is required.

Though not prompted, consider what the time and space complexity is for heap_down. Does it differ from heap_up at all? What impact does the recursive call have on the complexity? Could this be improved?

[anselrognlie]

👀 What are the time and space complexities for heap_sort?

Your approach looks good. To heap sort, we build a heap from the data to be sorted, then we remove the values from the heap, which gives them back to us in order. What does this mean for the time and space complexity?

[anselrognlie]

Note the since this isn't a fully in-place solution (the MinHeap has a O(n) internal store), we don't necessarily need to modify the passed in list. The tests are written to check the return value, so we could unpack the heap into a new result list to avoid mutating the input.

    result = []
    while not heap.empty():
        result.append(heap.remove())

    return result